A control method for hydraulic servo system of excavator based on fuzzy flow parameter

Abstract

The application discloses a kind of based on fuzzy flow parameter's excavator hydraulic servo system control method, mainly related to excavator automatic control technical field, specifically refers to a kind of based on fuzzy flow parameter's excavator hydraulic servo system control method.The application is by collecting the valve opening degree of excavator multi-joint linkage, excavator arm, bucket stick, bucket, through valve control hydraulic cylinder continuity equation and force balance equation, accurately calculate the flow distribution to three joints of excavator in multi-joint linkage, i.e. the load flow of three joints.According to valve opening degree and load flow, construct fuzzy control rule table, calculate fuzzy parameter, summarize fuzzy control rule.According to fuzzy control rule, adopt the sliding mode control based on exponential approach rate, calculate system control rate, correct the control amount of system controller, improve the control precision of system without installing flow sensor, reduce cost.

Description

Technical Field

[0001] This invention relates to the field of excavator control technology, mainly to the field of excavator automatic control technology, specifically to a control method for an excavator hydraulic servo system based on fuzzy flow parameters. Background Technology

[0002] With the continuous development of science and technology, automation technology has been widely applied in various fields. The construction machinery industry is also facing transformation and upgrading towards automation. The development of excavator automation has not only improved the labor intensity of workers and overcome harsh construction conditions, but also improved work efficiency and quality.

[0003] In recent years, excavator automatic control technology has developed rapidly. However, most current excavator electro-hydraulic control systems are modeled based on single-cylinder models, rarely involving linkage. But the actual hydraulic system is a multi-variable coupled system. Because the total flow rate of the oil supply pipeline is limited, the oil pressure is restricted. When the flow rate exceeds the upper limit, the flow rate entering each joint decreases. Furthermore, to achieve functions such as linear travel, swing priority, travel pressure boosting, merging, and regeneration, complex circuit structures are used. When multiple joints are linked, the flow rates of each joint are coupled, making it difficult to accurately calculate the flow rate allocated to each joint. This leads to changes in model parameters and increases the difficulty of control. At the same time, each excavator differs due to manufacturing and assembly errors, and the pre-shipment debugging process also results in different overall machine control parameters. Therefore, even excavator models of the same model do not have completely identical model parameters. Summary of the Invention

[0004] This invention addresses the problem that existing excavator electro-servo hydraulic systems struggle to accurately calculate the flow rate allocated to each joint during multi-joint linkage, thus affecting system control accuracy. It provides a control method for excavator hydraulic servo systems based on fuzzy flow parameters.

[0005] A control method for an excavator hydraulic servo system based on fuzzy flow parameters, comprising:

[0006] S1. Set key points: Install angle sensors at the three joints of the excavator: boom, stick, and bucket, to obtain the absolute angle data of the three joints, and calculate the joint angles based on the absolute angle data;

[0007] S2. Calculate the linear displacement of the cylinder piston of the corresponding joint based on the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston.

[0008] S3. Calculate the load flow rate based on the joint angle and the linear displacement of the cylinder piston using the continuity equation and force balance equation of the valve-controlled hydraulic cylinder;

[0009] S4. Obtain the valve opening corresponding to different load flow rates, and summarize fuzzy control rules based on the valve opening and load flow rate;

[0010] S5. Construct a multiple-input multiple-output (MIMO) model, calculate the system model parameters according to fuzzy control rules, and correct the output control quantity of the system model;

[0011] S6. Sliding mode control of the excavator hydraulic servo system is performed based on the output control quantity of the modified system model.

[0012] In S1, the key points are set as follows: point O is the connection between the excavator body and the boom; point A is the connection between the boom hydraulic cylinder and the body; point B is the connection between the boom hydraulic cylinder and the boom; point C is the connection between the stick hydraulic cylinder and the boom; point D is the connection between the stick hydraulic cylinder and the stick; point E is the connection between the bucket hydraulic cylinder and the stick; point I is the connection between the bucket hydraulic cylinder, the rocker arm, and the connecting rod; point G is the connection between the rocker arm and the stick; point J is the connection between the connecting rod and the stick; point H is the connection between the bucket and the stick; and point L is the tip of the bucket teeth.

[0013] Angle sensors are installed at the boom, stick, and bucket joints of the excavator. The angle sensor at the boom joint is parallel to BE, the angle sensor at the stick joint is parallel to EH, and the angle sensor at the bucket joint is parallel to GI. The data acquired by the angle sensors are the angles between the three joints and the horizontal plane, representing the absolute angles of the three joints, denoted as θ. 10 θ 20 θ 30 Construct a DH coordinate system, transform the absolute angle data of the three joints of the excavator according to the DH method, and record the transformed absolute angle data of the three joints of the excavator as θ1, θ2, and θ3 respectively. Calculate the joint angles of the three joints of the excavator based on the DH transformed angle data.

[0014] In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is as follows:

[0015]

[0016] ∠AOB=∠EOB+θ1+∠AOx;

[0017]

[0018] ∠CED=π-∠CEO-∠HED+θ2;

[0019]

[0020] ∠FGI=2π-∠FGE-∠EGH-∠HGI;

[0021] In the formula, π dB x dA x dBu These represent the linear displacements of the hydraulic cylinder pistons corresponding to the three joints of the boom, stick, and bucket, where π is a horizontal angle and l is a vertical angle. OA l OB Let ∠AOB and ∠EOB be the distances from point O to points A and B, respectively, and ∠AOB and ∠EOB be the angles between lines AO and EO and OB, respectively. ∠AOx is the angle between line AO ​​and the horizontal direction x. CE l DE Let be the distances from points C and D to point E, respectively; ∠CED is the angle between lines CE and ED; ∠CEO is the angle between lines CE and EO; and ∠HED is the angle between lines HE and ED. FG l IG Let F and I be the distances from point F and point I to point G, respectively. Let ∠FGI be the angle between lines FG and GI, ∠FGE be the angle between lines FG and GE, ∠EGH be the angle between lines EG and GH, and ∠HGI be the angle between lines HG and GI.

[0022] In S3, the continuity equation for the valve-controlled hydraulic cylinder is:

[0023]

[0024] p L =p1-np2;

[0025]

[0026] In the formula, Q1 is the flow rate entering the hydraulic cylinder, d() is the derivative, and x d Let dt be the linear displacement of the cylinder piston, and C be the time step. i C is the internal leakage coefficient. e C is the external leakage coefficient. iL C is the equivalent leakage coefficient. es To add a leakage coefficient, p1 and p2 are the oil pressures in the rodless and rod chambers of the hydraulic cylinder, respectively, and β e V1 is the effective bulk modulus, and V1 is the volume of the rodless chamber of the hydraulic cylinder. p is the first derivative of the linear displacement of the cylinder piston. L p is the load pressure of the hydraulic cylinder. s For oil source pressure, For equivalent volume, The equivalent load pressure is given by n, the flow ratio is given by A1 and A2, and the piston areas of the rodless and rod chambers of the hydraulic cylinder are given by Q. L For load flow, C d Let X be the flow coefficient of the spool valve, ω be the area gradient of the spool valve, and X be the flow coefficient of the spool valve.v ρ represents the valve opening degree, and ρ represents the pressure oil density.

[0027] In S3, the force balance equation is:

[0028]

[0029] In the formula, Let M be the second derivative of the linear displacement of the cylinder piston, and B be the load mass. p Where F is the viscous damping coefficient, K is the elastic coefficient, and F is the viscous damping coefficient. l External interference force;

[0030] Based on the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow rate is:

[0031]

[0032] K F The fuzzy parameter represents the degree of influence between the three joints during joint linkage. The fuzzy parameter is calculated using the maximum membership average method. The fuzzy parameter is divided into five levels: very small influence (VS), small influence (S), medium influence (M), large influence (L), and very large influence (VL).

[0033] In S4, the valve opening is divided into three levels: small opening (SD), medium opening (MD), and large opening (LD). Handle commands are input to one of the three joints of the excavator boom, stick, and bucket. Based on the valve opening of the other two joints, triangular membership functions are constructed, and the joint membership degrees corresponding to different valve opening levels of the other two joints are calculated. The Mamdani fuzzy control algorithm is used to calculate the fuzzy parameters of the joint that inputs the handle command based on the joint membership degrees of the other two joints. Fuzzy control rules are summarized, and a fuzzy control rule table is constructed.

[0034] Construct a multiple-input multiple-output (MIMO) model, defining the input matrix x and output matrix y as follows:

[0035]

[0036] In the formula, x i , i = 1, 2, 3…9, represents the i-th input parameter of the system; x represents the first derivative of the i-th input parameter of the system; dB x dA x dBu The linear displacements v of the hydraulic cylinder pistons of the boom, stick, and bucket are respectively. dB v dA v dBu The linear displacement velocities of the hydraulic cylinder pistons of the boom, stick, and bucket are respectively, a dB a dA a dBuThese are the linear displacement accelerations of the pistons in the hydraulic cylinders of the boom, stick, and bucket, respectively; a 1n m = 1, 2, 3, representing the nominal value of the m-th sub-model of the system; a 2n m = 1, 2, 3, representing the model parameters of the m-th sub-model of the system; d n m = 1, 2, 3, representing the external disturbance of the m-th sub-model of the system; u m m = 1, 2, 3, representing the control law of the m-th sub-model of the system, and sgn() is the sign function.

[0037] In S6, the synovial surface s is:

[0038] s = C1e1 + C2e2 + e3;

[0039]

[0040] In the formula, C1>0, C2>0, C1 and C2 are error coefficients, e1 is the tracking error, and e2 and e3 are the definition errors. These are the first-order differentials of the linear displacements of the cylinder pistons of the boom, stick, and bucket, respectively. These are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints: boom, stick, and bucket.

[0041] Differential calculations are performed on the synovial surface s to obtain

[0042]

[0043] In the formula, The first derivative of the tracking error, To define the first differential of the error, These are the third-order differential values ​​of the linear displacements of the hydraulic cylinder pistons corresponding to the boom, stick, and bucket joints, respectively; g(x) v ) m m = 1, 2, 3, representing the output of the m-th sub-model of the system, and g(x) is the system output; Let x represent the first derivative of the external disturbance force, u be the control law of the system, and x be the first derivative of the external disturbance force. vV x vA x vBu These represent the valve openings corresponding to the three joints: boom, stick, and bucket, respectively. a1 is the system nominal value matrix; a2 is the system model parameter matrix.

[0044] right Sliding mode control based on exponential reaching rate is employed:

[0045]

[0046] y = Cx + Du;

[0047] In the formula, ε>0, k c >0, ε represents the control parameter, k c Let x represent the leakage coefficient, and x be the input matrix. The first-order differential matrix of the input matrix, y is the output matrix, A is the input coefficient, B is the input control coefficient, C is the output coefficient, and D is the output control coefficient;

[0048] The control law u of the system is:

[0049]

[0050] The initial control rate u of the system is obtained from the input preset trajectory. During the actual control process of the system, the fuzzy flow parameters are calculated in real time, and the control rate of the system is updated in real time accordingly.

[0051] Compared to existing technologies, this invention offers the following advantages: By collecting data on the valve openings of the boom, stick, and bucket during multi-joint operation of an excavator, and using the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, this invention accurately calculates the flow rate distributed to the three joints during multi-joint operation, i.e., the load flow rate of the three joints. Based on the valve openings and load flow rates, a fuzzy control rule table is constructed, fuzzy parameters are calculated, and fuzzy control rules are summarized. Based on these fuzzy control rules, sliding mode control based on exponential reaching law is employed to calculate the system control rate and correct the control quantity of the system controller, thereby improving the system's control accuracy. Furthermore, this invention collects excavator joint angle data using angle sensors. Based on the conversion relationship between the joint angle and the linear displacement of the corresponding joint's cylinder piston, the linear displacement of the cylinder piston is calculated. Then, the joint load flow rate is calculated using the continuity equation and force balance equation of the valve-controlled hydraulic cylinder. Therefore, the system does not require the installation of flow sensors during application, reducing application costs. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the installation position of the angle sensor and a schematic diagram of the key point setting position in S1 provided in the embodiment of the present invention;

[0053] Figure 2 A system control flowchart of a hydraulic servo system control method for an excavator based on fuzzy flow parameters is provided in an embodiment of the present invention.

[0054] Figure 3 A data graph of the linear velocity of the hydraulic cylinder piston of the boom joint, collected when the excavator boom command 700 is issued, provided for an embodiment of the present invention.

[0055] Figure 4This is a data graph showing the linear velocity of the piston of the hydraulic cylinder corresponding to the joint linkage during the excavator boom command 700, stick command 200, and bucket command 300 provided in an embodiment of the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] A control method for an excavator hydraulic servo system based on fuzzy flow parameters, comprising:

[0058] S1. Set key points: Install angle sensors at the three joints of the excavator: boom, stick, and bucket, to obtain the absolute angle data of the three joints, and calculate the joint angles based on the absolute angle data;

[0059] S2. Calculate the linear displacement of the cylinder piston of the corresponding joint based on the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston.

[0060] S3. Calculate the load flow rate based on the joint angle and the linear displacement of the cylinder piston using the continuity equation and force balance equation of the valve-controlled hydraulic cylinder;

[0061] S4. Obtain the valve opening corresponding to different load flow rates, and summarize fuzzy control rules based on the valve opening and load flow rate;

[0062] S5. Construct a multiple-input multiple-output (MIMO) model, calculate the system model parameters according to fuzzy control rules, and correct the output control quantity of the system model;

[0063] S6. Sliding mode control of the excavator hydraulic servo system is performed based on the output control quantity of the modified system model.

[0064] In S1, the key points are set as follows: point O is the connection between the excavator body and the boom; point A is the connection between the boom hydraulic cylinder and the body; point B is the connection between the boom hydraulic cylinder and the boom; point C is the connection between the stick hydraulic cylinder and the boom; point D is the connection between the stick hydraulic cylinder and the stick; point E is the connection between the bucket hydraulic cylinder and the stick; point I is the connection between the bucket hydraulic cylinder, the rocker arm, and the connecting rod; point G is the connection between the rocker arm and the stick; point J is the connection between the connecting rod and the stick; point H is the connection between the bucket and the stick; and point L is the tip of the bucket teeth.

[0065] Angle sensors are installed at the boom, stick, and bucket joints of the excavator. The angle sensor at the boom joint is parallel to BE, the angle sensor at the stick joint is parallel to EH, and the angle sensor at the bucket joint is parallel to GI. The data acquired by the angle sensors are the angles between the three joints and the horizontal plane, representing the absolute angles of the three joints, denoted as θ. 10 θ 20 θ 30 Construct a DH coordinate system, transform the absolute angle data of the three joints of the excavator according to the DH method, and record the transformed absolute angle data of the three joints of the excavator as θ1, θ2, and θ3 respectively. Calculate the joint angles of the three joints of the excavator based on the DH transformed angle data.

[0066] In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is as follows:

[0067]

[0068] ∠AOB=∠EOB+θ1+∠AOx;

[0069]

[0070] ∠CED=π-∠CEO-∠HED+θ2;

[0071]

[0072] ∠FGI=2π-∠FGE-∠EGH-∠HGI;

[0073] In the formula, x dB x dA x dBu These represent the linear displacements of the hydraulic cylinder pistons corresponding to the three joints of the boom, stick, and bucket, where π is a horizontal angle and l is a vertical angle. OA l OB Let ∠AOB and ∠EOB be the distances from point O to points A and B, respectively, and ∠AOB and ∠EOB be the angles between lines AO and EO and OB, respectively. ∠AOx is the angle between line AO ​​and the horizontal direction x. CE l DE Let be the distances from points C and D to point E, respectively; ∠CEO is the angle between lines CE and ED; ∠CEO is the angle between lines CE and EO; ∠HED is the angle between lines HE and ED. FG l IGPoints F and I represent the distances from point F and point I to point G, respectively. ∠FGI is the angle between lines FG and GI, ∠FGE is the angle between lines FG and GE, ∠EGH is the angle between lines EG and GH, and ∠HGI is the angle between lines HG and GI. Points A to L are the data points for the three joints of the excavator, and the data locations are as follows: Figure 1 As shown, the DH conversion angle data in S1 is differentiated to obtain the angular velocities of the three joints of the excavator. Combined with the joint angles and the lengths of the joint components, the distance between the data points of the excavator is calculated.

[0074] In S3, the continuity equation for the valve-controlled hydraulic cylinder is:

[0075]

[0076] In the formula, Q1 is the flow rate entering the hydraulic cylinder, d() is the derivative, and x d Let dt be the linear displacement of the cylinder piston, and C be the time step. i C is the internal leakage coefficient. e C is the external leakage coefficient. iL C is the equivalent leakage coefficient. es To add a leakage coefficient, p1 and p2 are the oil pressures in the rodless and rod chambers of the hydraulic cylinder, respectively, and β e V1 is the effective bulk modulus, and V1 is the volume of the rodless chamber of the hydraulic cylinder. p is the first derivative of the linear displacement of the cylinder piston. L p is the load pressure of the hydraulic cylinder. s For oil source pressure, For equivalent volume, The equivalent load pressure is given by n, the flow ratio is given by A1 and A2, and the piston areas of the rodless and rod chambers of the hydraulic cylinder are given by Q. L For load flow, C d Let ω be the flow coefficient of the spool valve, ω be the area gradient of the spool valve, and x be the flow coefficient of the spool valve. v ρ represents the valve opening degree, and ρ represents the pressure oil density.

[0077] In S3, the force balance equation is:

[0078]

[0079] In the formula, Let M be the second derivative of the linear displacement of the cylinder piston, and B be the load mass. p Where F is the viscous damping coefficient, K is the elastic coefficient, and F is the viscous damping coefficient. l External interference force;

[0080] Based on the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow rate is:

[0081]

[0082] K F The fuzzy parameter represents the degree of influence between the three joints during joint linkage. The fuzzy parameter is calculated using the maximum membership average method. The fuzzy parameter is divided into five levels: very small influence (VS), small influence (S), medium influence (M), large influence (L), and very large influence (VL).

[0083] In S4, valve opening is divided into three levels: small (SD), medium (MD), and large (LD). A handle command is input to one of the three joints of the excavator boom, stick, and bucket. Based on the valve openings of the other two joints, triangular membership functions are constructed, and the joint membership degrees corresponding to different valve opening levels of the other two joints are calculated. The Mamdani fuzzy control algorithm is used to calculate the fuzzy parameters of the joint receiving the handle command based on the joint membership degrees of the other two joints. Fuzzy control rules are summarized, and a fuzzy control rule table is constructed. Taking the extension of the excavator boom hydraulic cylinder as an example, when the handle command for extending the excavator boom is input, the linear position x of the piston in the excavator boom shutdown cylinder is calculated. dB The valve openings of the excavator's boom and bucket are collected and recorded as x. vA x vBu Using triangular membership functions, calculate the joint membership degrees of the boom and bucket for different valve levels. The boom membership degree is denoted as μ according to the valve level. SA μ MA μ LA The membership degree of the bucket is recorded as μ. SBu μ MBu μ LBu Based on the valve opening and joint membership degree, fuzzy parameters are calculated and then substituted into the load flow calculation equation to calculate the load Q of the excavator boom extension corresponding to different valve levels. LB A fuzzy control rule table was constructed, and the fuzzy control rule table corresponding to the extension of the boom was extracted, as shown in Table 1.

[0084] Table 1. Fuzzy Control Rules for Excavator Boom Extension

[0085]

[0086] In the table, K FB To extract the fuzzy parameters corresponding to the boom extension command, SD A MD A LD A The three levels of valve opening for the boom joint, SD Bu MD Bu LD BuTable 1 shows the three levels of valve opening for the bucket joint: VS, S, M, L, and VL, representing the degree of influence of the excavator stick and bucket on the excavator boom when the boom is extended. As can be seen from Table 1, x... vA x vBu The larger K is F The larger; x vA x vBu Moderate, K F Moderate; x vA x vBu The smaller K is F The smaller the value, the better. Based on the nine fuzzy control rules from VS(1) to VL(9), the output fuzzy quantity is calculated using the output fuzzy quantity calculation formula to obtain the fuzzy parameters.

[0087] The formula for calculating the output fuzzy quantity is as follows: In the output control formula, U * To output the sum of fuzzy values, j = 1, 2, 3…9 represents the nine fuzzy control rules in the fuzzy control rule table. To obtain the union of the nine fuzzy control rules, For the large-small synthesis method, R j For the implication relation of each fuzzy rule, () T Indicates matrix transpose. This represents the membership degree of each fuzzy rule. The same principle applies when the boom retracts, as well as the stick and bucket.

[0088] Construct a multiple-input multiple-output (MIMO) model, defining the input matrix x and output matrix y as follows:

[0089]

[0090] In the formula, x i , i = 1, 2, 3…9, represents the i-th input parameter of the system; x represents the first derivative of the i-th input parameter of the system; dB x dA x dBu The linear displacements v of the hydraulic cylinder pistons of the boom, stick, and bucket are respectively. dB v dA v dBu The linear displacement velocities of the hydraulic cylinder pistons of the boom, stick, and bucket are respectively, a dB a dA a dBu These are the linear displacement accelerations of the pistons in the hydraulic cylinders of the boom, stick, and bucket, respectively; a 1m m = 1, 2, 3, representing the nominal value of the m-th sub-model of the system; a 2m m = 1, 2, 3, representing the model parameters of the m-th sub-model of the system; d mm = 1, 2, 3, representing the external disturbance of the m-th sub-model of the system; u m Let m = 1, 2, 3, representing the control law of the m-th sub-model of the system, and sgn() be the sign function. The system control model provided in the experimental embodiment of this invention includes 3 sub-models, a 21

[0091] In S6, the synovial surface s is:

[0092] s = C1e1 + C2e2 + e3;

[0093]

[0094] In the formula, C1>0, C2>0, C1 and C2 are error coefficients, e1 is the tracking error, and e2 and e3 are the definition errors. These are the first-order differentials of the linear displacements of the cylinder pistons of the boom, stick, and bucket, respectively. These are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints: boom, stick, and bucket.

[0095] Differential calculations are performed on the synovial surface s to obtain

[0096]

[0097] In the formula, The first derivative of the tracking error, To define the first differential of the error, These are the third-order differential values ​​of the linear displacements of the hydraulic cylinder pistons corresponding to the boom, stick, and bucket joints, respectively; g(x) v ) m m = 1, 2, 3, representing the output of the m-th sub-model of the system, and g(x) is the system output; Let x represent the first derivative of the external disturbance force, u be the control law of the system, and x be the first derivative of the external disturbance force. vB x vA x vBu These represent the valve openings corresponding to the three joints: boom, stick, and bucket, respectively. a1 is the system nominal value matrix; a2 is the system model parameter matrix.

[0098] right Sliding mode control based on exponential reaching rate is employed:

[0099]

[0100] y = Cx + Du;

[0101] In the formula, ε>0, k c >0, ε represents the control parameter, k cLet x represent the leakage coefficient, and x be the input matrix. The first-order differential matrix of the input matrix, y is the output matrix, A is the input coefficient, B is the input control coefficient, C is the output coefficient, and D is the output control coefficient;

[0102] The control law u of the system is:

[0103]

[0104] The initial control rate u of the system is obtained from the input preset trajectory. During the actual control process of the system, the fuzzy flow parameters are calculated in real time, and the control rate of the system is updated in real time accordingly.

[0105] like Figure 1 The key points shown are: point O is the connection between the excavator body and the boom; point A is the connection between the boom hydraulic cylinder and the body; point B is the connection between the boom hydraulic cylinder and the boom; point C is the connection between the stick hydraulic cylinder and the boom; point D is the connection between the stick hydraulic cylinder and the stick; point E is the connection between the boom and the stick; point F is the connection between the bucket hydraulic cylinder and the stick; point I is the connection between the bucket hydraulic cylinder and the rocker arm and connecting rod; point G is the connection between the rocker arm and the stick; point J is the connection between the connecting rod and the stick; point H is the connection between the bucket and the stick; and point L is the tip of the bucket teeth. Angle sensors are installed at the three joints of the excavator boom, stick, and bucket. The angle sensor at the boom joint is parallel to BE; the angle sensor at the stick joint is parallel to EH; and the angle sensor at the bucket joint is parallel to GI. The angle sensors collect the angles between the three joints and the horizontal direction, obtaining the absolute angle data of the three joints. The absolute angle data of the three joints are denoted as θ. 10 θ 20 θ 30 A kinematic coordinate system, DH coordinate system, is constructed and denoted as θ1, θ2, and θ3, respectively. The joint angles of the excavator are calculated based on the DH-transformed angle data. Differential calculations are performed on the DH-transformed angle data to obtain the joint angular velocities of the three joints of the excavator. Combined with the joint angles and the lengths of the joint components, the distances between the data points of the three joints are calculated. Based on the transformation relationship between the excavator joint angles and the linear displacements of the joint cylinder pistons in S2, the linear displacements of the cylinder pistons of the three joints of the excavator are calculated. Substituting the linear displacements of the cylinder pistons of the three joints into the continuity equation of the valve-controlled hydraulic cylinder in S3, the flow rate flowing into the corresponding joint hydraulic cylinder can be obtained, and thus the load flow rate of that joint can be determined.

[0106] Figure 2This invention provides a system control flowchart for a hydraulic servo system control method for an excavator based on fuzzy flow parameters. After the excavator starts, the system begins operation, reads the input preset trajectory, obtains the initial control rate u based on the input preset trajectory, and performs sliding control on the excavator's hydraulic servo system. During the control process, the system calculates the joint angles according to the DH method based on data collected by the angle sensor, calculates the load flow in real time through the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, and determines whether the flow limit is exceeded. If the flow limit is exceeded, fuzzy flow calculation is performed for each joint, fuzzy rules are summarized, and model parameters are modified. If the limit is not exceeded, the model parameters corresponding to the input preset trajectory are used as the system model parameters to control the system. The system checks whether the endpoint has been reached. If not, a new round of sliding control is started; if the endpoint has been reached, the system ends control.

[0107] Figure 3 This is a data graph of the linear velocity of the hydraulic cylinder piston of the boom joint, collected when the excavator boom command 700 is issued, provided in an embodiment of the present invention. Figure 4 The data graph showing the linear velocity of the piston in the hydraulic cylinder of the corresponding joint during joint linkage when the excavator boom command 700, stick command 200, and bucket command 300 are obtained in an embodiment of the present invention shows that, according to the continuity equation of the valve-controlled hydraulic cylinder, the larger the linear displacement of the cylinder piston, the greater the flow rate into the hydraulic cylinder, and the greater the load flow rate of the corresponding joint. Figure 3 and Figure 4 The linear velocity of the hydraulic cylinder piston is the linear displacement velocity of the piston. The "-" sign only indicates the direction of the piston's linear displacement velocity, not its magnitude. The magnitude of the piston's linear displacement velocity is its absolute value. The absolute value of the piston's linear displacement velocity directly reflects the magnitude of the piston's linear displacement at the corresponding joint at that moment, and thus reflects the magnitude of the load flow at that joint. In other words, the greater the piston's linear velocity, the greater the load flow at the corresponding joint. Through comparison... Figure 3 and Figure 4 It can be seen that when the excavator boom command is 700, the linear displacement velocity of the hydraulic cylinder piston of the excavator boom joint during joint linkage is ( Figure 4 The linear displacement velocity of the hydraulic cylinder piston in the excavator boom joint is significantly smaller than that when there is no joint linkage. Figure 3 Therefore, in the joint linkage of the excavator boom command 700, stick command 200, and bucket command 300, the total flow of the three joints of the excavator boom, stick, and bucket exceeds the maximum value, resulting in a reduction in the flow entering each joint. It is necessary to calculate the fuzzy flow parameters and adjust the system control quantity.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A control method for an excavator hydraulic servo system based on fuzzy flow parameters, characterized in that, include: S1. Set key points: Install angle sensors at the three joints of the excavator: boom, stick, and bucket, to obtain the absolute angle data of the three joints, and calculate the joint angles based on the absolute angle data; S2. Calculate the linear displacement of the cylinder piston of the corresponding joint based on the conversion relationship between the joint angle and the linear displacement of the joint cylinder piston. S3. Calculate the load flow rate based on the joint angle and the linear displacement of the cylinder piston using the continuity equation and force balance equation of the valve-controlled hydraulic cylinder; S4. Obtain the valve opening corresponding to different load flow rates, and summarize fuzzy control rules based on the valve opening and load flow rate; S5. Construct a multiple-input multiple-output (MIMO) model, calculate the system model parameters according to fuzzy control rules, and correct the output control quantity of the system model; S6. Sliding mode control of the excavator hydraulic servo system is performed based on the output control quantity of the modified system model.

2. The control method for an excavator hydraulic servo system based on fuzzy flow parameters according to claim 1, characterized in that, In S1, the key points are set as follows: point O is the connection between the excavator body and the boom; point A is the connection between the boom hydraulic cylinder and the body; point B is the connection between the boom hydraulic cylinder and the boom; point C is the connection between the stick hydraulic cylinder and the boom; point D is the connection between the stick hydraulic cylinder and the stick; point E is the connection between the bucket hydraulic cylinder and the stick; point I is the connection between the bucket hydraulic cylinder, the rocker arm, and the connecting rod; point G is the connection between the rocker arm and the stick; point J is the connection between the connecting rod and the stick; point H is the connection between the bucket and the stick; and point L is the tip of the bucket teeth. Angle sensors are installed at the boom, stick, and bucket joints of the excavator. The angle sensor at the boom joint is parallel to BE, the angle sensor at the stick joint is parallel to EH, and the angle sensor at the bucket joint is parallel to GI. The data acquired by the angle sensors are the angles between the three joints and the horizontal plane, representing the absolute angles of the three joints, denoted as _____. , , Construct a DH coordinate system, transform the absolute angle data of the three joints of the excavator according to the DH method, and record the transformed absolute angle data of the three joints of the excavator as follows: , , The joint angles of the three joints of the excavator are calculated based on the DH conversion angle data.

3. The control method for an excavator hydraulic servo system based on fuzzy flow parameters according to claim 2, characterized in that, In S2, the conversion relationship between the excavator joint angle and the linear displacement of the joint cylinder piston is as follows: ； ； ； ； ； ； In the formula, , , These represent the linear displacements of the hydraulic cylinder pistons corresponding to the three joints: boom, stick, and bucket. It is a straight angle. , Let O be the distance from point A and point B, respectively. , These are the angles between lines AO and EO and OB, respectively. The straight line AO ​​and the horizontal direction The angle between them , Let C and D be the distances from point E, respectively. The angle between lines CE and ED is... Let be the angle between lines CE and EO. The angle between lines HE and ED is... , Let F and I be the distances from point F and point I to point G, respectively, and ∠FGI be the angle between lines FG and GI. The angle between lines FG and GE. ∠G is the angle between lines EG and GH, and ∠HGI is the angle between lines HG and GI.

4. The control method for an excavator hydraulic servo system based on fuzzy flow parameters according to claim 3, characterized in that, In S3, the continuity equation for the valve-controlled hydraulic cylinder is: ； ； ； In the formula, The flow rate entering the hydraulic cylinder, To find the derivative, This represents the linear displacement of the cylinder piston. For time step, The internal leakage coefficient, The external leakage coefficient, The equivalent leakage coefficient, To add a leakage factor, , These refer to the oil pressure in the rodless chamber and the rod chamber of the hydraulic cylinder, respectively. For effective bulk modulus, This refers to the volume of the rodless chamber of the hydraulic cylinder. = It is the first derivative of the linear displacement of the cylinder piston; The load pressure of the hydraulic cylinder. For oil source pressure, For equivalent volume, For equivalent load pressure, For flow ratio, , These are the piston areas of the rodless chamber and the rod chamber of the hydraulic cylinder, respectively. For load traffic, The flow coefficient of the slide valve. For the area gradient of the slide valve, For valve opening, The density is the pressure oil.

5. The excavator hydraulic servo system control method based on fuzzy flow parameters according to claim 4, characterized in that, In S3, the force balance equation is: ； In the formula, Let be the second derivative of the linear displacement of the cylinder piston. For load quality, The viscous damping coefficient is... The elastic coefficient, External interference force; Based on the continuity equation and force balance equation of the valve-controlled hydraulic cylinder, the load flow rate is: ； The fuzzy parameter represents the degree of influence between the three joints during joint linkage. The fuzzy parameter is calculated using the maximum membership average method. The fuzzy parameter is divided into five levels: very small influence (VS), small influence (S), medium influence (M), large influence (L), and very large influence (VL).

6. The excavator hydraulic servo system control method based on fuzzy flow parameters according to claim 5, characterized in that, In S4, the valve opening is divided into three levels: small opening (SD), medium opening (MD), and large opening (LD). Handle commands are input to one of the three joints of the excavator boom, stick, and bucket. Based on the valve opening of the other two joints, triangular membership functions are constructed, and the joint membership degrees corresponding to different valve opening levels of the other two joints are calculated. The Mamdani fuzzy control algorithm is used to calculate the fuzzy parameters of the joint that inputs the handle command based on the joint membership degrees of the other two joints. Fuzzy control rules are summarized, and a fuzzy control rule table is constructed.

7. The excavator hydraulic servo system control method based on fuzzy flow parameters according to claim 6, characterized in that, Construct a multiple-input multiple-output (MIMO) model, defining the input matrix x and output matrix y as follows: ， ； , , , , , ， ； ； ； ， ； ； In the formula, , indicating the system's first One input parameter; , indicating the system's first The first derivative of each input parameter; , These are the linear displacements of the hydraulic cylinder pistons for the boom, stick, and bucket, respectively. , , These are the linear displacement velocities of the hydraulic cylinder pistons for the boom, stick, and bucket, respectively. , , These are the linear displacement accelerations of the pistons in the hydraulic cylinders of the boom, stick, and bucket, respectively. , , representing the nominal value of the m-th sub-model of the system; , , representing the model parameters of the m-th sub-model of the system; , , representing the external disturbance of the m-th sub-model of the system; , , representing the control law of the m-th sub-model of the system. It is a symbolic function; , , indicating the system's first The output of each sub-model.

8. The control method for an excavator hydraulic servo system based on fuzzy flow parameters according to claim 7, characterized in that, In S6, the synovial surface for: ； ； ； ； In the formula, , , The error coefficient, To track errors, , To define the error, , These are the first-order differentials of the linear displacements of the cylinder pistons of the boom, stick, and bucket, respectively. , , These are the second-order differentials of the linear displacements of the cylinder pistons corresponding to the three joints: boom, stick, and bucket.

9. A control method for an excavator hydraulic servo system based on fuzzy flow parameters according to claim 8, characterized in that, For the synovial surface Differential calculations are performed to obtain : ； ; ； ； ； In the formula, The first derivative of the tracking error, , To define the first differential of the error, , , These are the third-order differential values ​​of the linear displacement of the cylinder pistons corresponding to the three joints of the boom, stick, and bucket, respectively. For system output; The first derivative of the external disturbance force, For the control law of the system, , , These represent the valve openings corresponding to the boom, stick, and bucket joints, respectively. This is the system nominal value matrix; This is the system model parameter matrix.

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